Your kidneys are shaped like beans and are about the size of your fist. They play a vital role in keeping the chemicals and water in your body balanced. Your urinary system removes a waste called urea from your blood after the food you eat is broken down in your body. Problems can occur in your kidneys and urinary system from aging, from illnesses or from injury. These problems can range from minor to life-threatening. If you're having kidney or urinary tract problems, you should see your doctor for an evaluation.